Shallow donor impurity of bismuth in silicon: Peculiar electrical properties of bismuth-related defects produced by electron irradiation

Electrical measurements are taken on bismuth-doped silicon subjected to electron irradiation at room temperature. The analysis of experimental data obtained in a temperature interval of 30–300 K shows a considerable decrease in the concentration of the shallow donor states of Bi in irradiated samples due to the formation of electrically neutral Bi-related complexes, which, in turn, are ascribed to bismuth–vacancy pairs. They are very stable up to T ≈ 300 °C. The contribution of radiation-produced acceptors in an irradiated material appears to be of minor importance. Unexpectedly, the behavior of the mobility of charge carriers in the course of irradiation and isochronal annealing displays very strange features. It is thought that this striking effect is accounted for by a split atomic configuration of bismuth–vacancy pairs, in sharp contrast to the well-known configuration of phosphorus–vacancy and arsenic–vacancy pairs.